A number of primary discrete emotions emerge over the first year of life. Little is known about the relation between facial signs of these affects and concomitant central nervous system processes. The research proposed in this application is designed to investigate three and ten month old infants' responses to facial and vocal expressions of happiness and sadness. It is novel, methodologically, in combining the precision of detailed coding procedures for the measurement of facial affect with sophisticated techniques for the analysis of noninvasively recorded brain activity. At both three and ten months of age infants will be exposed to three conditions: mother smiling and sad; happy and sad voice (with text); and laughter and crying. Brain electrical activity from left and right leads in the frontal, parietal, and temporal regions will be recorded. Facial behavior of the infant in response to each of the eliciting conditions will be coded with a standard facial action coding system. The research will focus on hemispheric asymmetry associated with the presence of different facial signs of discrete emotion. These findings will provide important information on the relation of central nervous system processes and affect in the first year of life.